Do Probiotics Interfere With Coumadin?

Probiotics are "friendly" bacteria that live naturally in the body, but do not cause disease 1. They keep harmful bacteria in check and help with digestion. Probiotics also occur in certain fermented foods, such as yogurt, and are available in supplements 1. Consult your doctor before consuming probiotic supplements or significant amounts of probiotic-containing foods if you also use the anticoagulant medication warfarin, commonly known as the brand Coumadin.

Probiotic Uses

Probiotics are available in various formulations 1. Different species of lactobacillus are common ingredients 2. Probiotic supplements containing lactobacillus may be effective for uses such as treating certain types of diarrhea, ulcerative colitis, irritable bowel syndrome and bacterial vaginal infections, according to U.S. National Library of Medicine website MedlinePlus 2.


Coumadin reduces the clotting ability of the blood, making it useful for preventing blood clots in people at risk. It also can stop existing clots from growing larger. Examples of risk factors for blood clots include having an irregular heart rhythm or having experienced a heart attack. If you take Coumadin, you need regular blood tests, including one called the international normalized ratio, or INR 3. The INR measures the time it takes for your blood to clot as compared to an average.

Primary Coumadin Risk

Taking Coumadin increases the risk of bleeding, and combining it with medications or supplements that have anticoagulant effects elevates the risk further. Probiotics do not have this effect 1. Authoritative websites do not caution against taking probiotic supplements when using Coumadin, but one potential issue calls for a consultation with your doctor beforehand.

Vitamin K

Research is scant on specific commercial probiotic formulations, notes 1. As of 2011, no studies have focused on people taking both Coumadin and probiotics, according to medical doctor Timothy S. Harlan at his Dr. Gourmet website 14. A potential problem involves the production of vitamin K by probiotic bacteria, cautions Harlan. Vitamin K increases blood clotting ability. If you take Coumadin, you need to keep vitamin K levels in your body relatively steady, because fluctuations may boost or interfere with the medication's effects. This doesn't necessarily mean you can't take probiotics when using Coumadin, but you may need closer blood monitoring at first and a change in your medication dosage 14.